1. Field of the Invention
The present invention relates in a general way to the field of mobile telephony and particularly to a multi-service mobile telephone network. More particularly, the present invention relates to a method for evaluating the performance of a second or third generation mobile telephone network based, for example, on the CDMA standard, on the CDMA 2000 standard, on the W-CDMA standard or on the EDGE standard (evolution of the GSM/GPRS mobile telephone network).
2. Description of the Related Art
When planning a network, designers are required to predict the performance of the network on the basis of geographical, data, the network configuration and the expected demand for service. Tools which simulate the operation of a network provide a practical method for planning the network. Network planning tools enable-designers to simulate the operation of various network configurations, and to modify the network on the basis of statistical data obtained as a result of the simulation.
The UMTS cellular network planning tools available at the present time are mostly based on simulations of the static type.
U.S. Pat. No. 6,111,857 describes a network planning tool in which the simulation is performed by using a set of databases containing terrain and population information associated with the market area over which the wireless network is configured. To perform the simulation, a composite propagation loss matrix and a demand and service vector are generated using the terrain and population information, as well as the configuration of the wireless telecommunications network. When the composite propagation loss matrix and the demand and service vector have been generated, an analysis of the reverse link is performed. Subsequently, an analysis of the forward link is performed. During both the reverse and forward link analysis the multiple iterations of analysis are performed until a stable result is achieved. Upon completion of the reverse and forward link analysis, the results of the simulation are displayed in a graphical manner for examination.
WO 03/003775 describes a wireless network planning tool which simulates wireless network operation, including subscriber admission processing, based on sophisticated reverse and forward link analyses that include data fallback procedures. Subscribers are associated with an application type, where each application type preferably has maximum and minimum data rates and one or more fallback rates. During simulation, the tool may use the fallback when evaluating forward and reverse communication links between subscribers and their associated sectors (base stations). A subscriber unable to close a reverse link to a given sector at a given data rate may be re-evaluated at a lower rate under the “fallback” procedures. Forward link analysis incorporates similar fallback procedures in forward link call admission.
Additionally, EP 1328131 A1 describes a method and a system for planning and/or evaluation of cell capacity in (CDMA) radio networks comprising at least one base station which defines at least one cell. The estimate of the cell capacity in the uplink and the estimation of the cell capacity in the downlink are both carried out by adding an amount of traffic (TBS1,1; TBS2,2) to the cell until a value representing the limit capacity (Lmin) is reached.
However, the applicant has observed that the performance of a mobile telephone network, for example a multi-service network, depends to a significant degree on the radio resource management (RRM) procedures and/or algorithms. This is because the radio resource management equipment included in the mobile telephone network require the use of a multiplicity of RRM procedures and/or algorithms, including, for example, those for admission control, congestion control, handover control, the control functions used when a user is in out-of-service conditions (“outage control”), the dynamic negotiation of the radio resource allocation, and power control. Moreover, the RRM procedures and/or algorithms may take into account, the various quality of service (QoS) requirements associated with the services.
The applicant has also observed that another fundamental aspect of the evaluation of the performance of a mobile telephone network is the characterization of the traffic imposed on the network by the various services involved. The traffic data are difficult to predict accurately, and are subject to extreme variability. In a process of planning and optimizing a mobile telephone network, therefore, it is often necessary, to evaluate the sensitivity of the network performance as a function of the variability of the traffic, and consequently to perform numerous simulations of the network to evaluate the impact of different traffic scenarios on the same network.
It is also known that there is a relationship between the simulation time and the accuracy of the simulation results. For example, in the case of a certain performance parameter of the network, the accuracy with which the network simulator can estimate this parameter depends on the number of statistic samples collected, and consequently on the duration of the simulation itself. A planning and optimization process may require the performance of a very large number of network simulations. Each simulation may, in turn, require the analysis of scenarios comprising a large number of users and base stations. The minimization of the simulation time is therefore a necessary condition for an efficient planning and optimization process.
On the other hand, there is a risk that such minimization may be carried out at the expense of the accuracy and reliability of the results of the simulations.
Dynamic simulators are generally used to evaluate the effect and/or impact of the RRM procedures and/or algorithms on the network performance and on network planning.
For example, WO 02/104055,in the name of the present applicant, describes a dynamic simulation system characterized by a modular structure based on interchangeable objects which can be selectively activated, and which comprise a simulation engine and a plurality of modules representing the equipment and elements of the network to be simulated. This structure enables the system to simulate highly complex networks.
However, the applicant has observed that the evaluation of the performance of a large network requires very long simulation times.
Recently, another simulation method has been proposed for evaluating the performance of a UMTS network on the basis of a short-term dynamic simulation (STD simulation) method, described for example in U. Türke, T. Winter, Ranjit Perera, E. Lamers, E. Meijerink, E. Fledderus and A. Serrador, “Comparison of different simulation approaches for cell performance evaluation”, Deliverable D2.2, IST project MOMENTUM, Oct. 13, 2002.
Short-term dynamic simulations (STD simulations) can be used to investigate the impact of mobility and the presence of different service configurations and to check that the quality of service (QoS) requirements are met. These simulations provide a larger amount of data on the behaviour of the system by comparison with simulations of the purely static type, since they take into consideration important dynamic effects such as the time-dependency requirements of the bit rate of the uplink and downlink, the increase and decrease of performance associated with “non real-time” data traffic, and the mobility of users.